1. Field of the Invention
The present invention relates generally to fluid-filled vibration-damping devices usable for engine mounts, body mounts, differential mounts and other mounts for automotive vehicles. More particularly, the present invention is concerned with novel manufacturing method and structure of a fluid-filled vibration-damping device capable of damping vibrations based on flows of non-compressible fluid sealed therein, or alternatively through a suitable control of pressure in the sealed fluid.
2. Description of the Related Art
A fluid-filled vibration-damping device is known as one type of vibration-damping device interposed between two components of a vibration system. The fluid-filled vibration-damping device includes: a first mounting member fixable to one of the two components; a second mounting member fixable to the other of the two components; a rubber elastic body elastically connecting the first and second mounting members while defining partially a fluid-filled zone in which non-compressible fluid is sealed. Such a known fluid-filled vibration-damping device is able to exhibit high vibration damping effect based on flows of non-compressible fluid or pressure control of the fluid, so that the known fluid-filled vibration-damping device has been expected to be used as an engine mount or other mounts for automotive vehicles.
Generally, such a fluid-filled vibration-damping device needs to provide high fluid-tight sealing at the fluid-filled zone after filling the fluid-filled zone with non-compressible fluid, to eliminate the likelihood of deterioration of an intended damping effect as a result of leakage of the non-compressible fluid from the fluid-filled zone.
A variety of sealing structures has been proposed in order to establish satisfactory fluid-tight sealing at the fluid-filled zone while facilitating filling of the fluid-filled zone with non-compressible fluid. According to one of the known sealing structures, a sealing part of the fluid-filled zone is at least partially configured such that a first sealing member of cylindrical configuration is fitted externally about and firmly assembled with a second sealing member with an annular fixing projection formed at one of the first and second sealing members being fluid-tightly, firmly fitted into a circumferential groove formed onto an inner or outer circumferential surface of the other of the first and second sealing members. Accordingly, the first and second sealing member is firmly fixed together with fluid-tightness.
More specifically, JP-A-61-189341 or JP-U-5-71490 disclose an example of the sealing structure as described above, wherein one of the two sealing members is constituted by a second mounting member of hollow cylindrical configuration whose opening at one axial end thereof is closed by the elastic body, and the other of the two sealing members is constituted by a cover member of shallow bottomed cylindrical shape. The cover member is situated on the side of the other axial end of the second mounting member such that open ends of the cover member and the second mounting member are butted together and caulked against to each other with a peripheral portion of a thin rubber layer interposed therebetween. Therefore, the other opening of the second mounting member is closed by the thin rubber layer, thereby providing the sealing structure illustrated above. Described in detail, a flange is formed at one of the open ends of the cover member and the second mounting member, while a caulking part is formed at the other open end so as to grip a periphery of the flange portion. The caulking part provides an annular fixing recess, and the flange portion provides an annular fixing projection, so that the flange portion is forcedly fitted into the flange portion, thereby accomplishing the above-described sealing structure in which the two sealing members are firmly fixed together with fluid-tightness.
Another example of the known sealing structure is disclosed in Japanese Patent Application No. 2001-215551 filed by the present assignee, in which one of the two sealing members is constituted by the second mounting member of hollow cylindrical configuration having an annular fixing projection formed at one open end peripheral portion thereof so as to protrudes radially inwardly, while the other of the two sealing members is constituted by a block shaped partition member having an annular fixing recess open in an outer circumferential surface thereof. The second mounting member is fitted externally about the partition member with its annular fixing projection firmly fitted into and held in engagement with the annular fixing recess of the partition member, with fluid-tightness.
In the known sealing structure as disclosed in JP-A-61-189341, JP-U-5-71490 and Japanese Patent Application No. 2001-215551, the two sealing members are fluid-tightly assembled together by axially inserting one of the two members into or onto the other, by utilizing a firmly fitting engagement of the annular fixing projection with the recess, thereby establishing advantageously desired fluid-tight sealing at the sealing part between the two sealing members. However, the known sealing structure has been prone to cause that on-compressible fluid has been sealed as residual liquid in the sealing part of the fluid-filled zone, in the course of assembly of components of the fluid-filled vibration-damping device within a mass of the non-compressible fluid, or during washing the device by means of a high-pressure liquid. If an obtained product contains residual liquid in the sealing part, the residual liquid may possibly leak out due to a change in ambient temperature and/or vibrations applied to the fluid-filled vibration-damping device. In this case, considerably difficult is a judgment as to whether the leakage of the fluid is due to an actual leakage of the non-compressible fluid from the fluid-filled zone or due to the leakage of the residual liquid in the sealing part. Therefore, a so-called “false leakage” of the fluid caused by the residual liquid leakage from the sealing part may give rise to anxiety about leakage of the sealed fluid from the fluid-filled zone, although the fluid-tight sealing at the fluid-sealing zone is kept at a desired level in actual.
To cope with the problem of the residual liquid as discussed above, one modified fluid-filled vibration-damping device has been proposed in JP-A-7-167200. In this modified device, a sealing part of a fluid-filled zone consists of a flange portion of a cover member and a caulking part formed at one open end peripheral portion of a second mounting member, which is caulked against to the flange portion, like in the above mentioned conventional devices. An improvement of the modified device is that the flange portion is provided with a groove so that the residual liquid remained in the sealing part effectively flows to the outside through the groove.
In this regards, a relatively small groove makes it difficult for the residual liquid to flow to the outside through the groove due to intermolecular forces, a gap vacuum, or the like. For this reason, the groove formed in the flange portion needs to have a relatively large size enough to establish a good discharge of the residual liquid through the groove. However, the larger the groove size, the greater the deterioration in fluid-tight sealing at the sealing part or in strength of the members. Accordingly, the modified fluid-filled vibration-damping device as proposed in JP-A-7-167200 has not yet been practical in mechanism of discharging residual liquid.